Tina McGuire breached a worldwide ban on revealing Jon Venables’s current identity by posting the picture.
This was as well as a name Venables was said to be using and the prison where he was allegedly being held.
McGuire, of Ammanford, Carmarthenshire, admitted contempt of court by breaching the 2001 injunction.
She was sentenced to eight months in prison, suspended for 15 months, and was also ordered to pay legal fees of £3,000 at a High Court hearing in London on Thursday.
The injunction bans the publication of anything purporting to reveal the identities, appearance or whereabouts of Venables and Robert Thompson.
They killed two-year-old James in February 1993 when they were aged 10, and have been living anonymously with new identities since being released from a life sentence.
Lord Justice Davis, sitting with Mrs Justice May, said the case against McGuire was “close to the line” for an immediate prison sentence.
But he added that in light of “the early, frank admission, the remorse, the stated and evidenced determination not to infringe again and the psychiatric report” the sentence could be suspended.
Katherine Hardcastle, representing the Solicitor General, previously told the court the case was brought for a post made by McGuire on a personal Facebook page on 20 February 2018.
The post was shared 627 times.
It was the second time she had attempted to post information purportedly about Venables, the court heard.
The court was told that in November 2017 McGuire posted on Facebook a picture purporting to be of Venables as an adult with a caption which encouraged others to “share this as much as possible as this photograph I posted this morning was removed”.
That post was shared nearly 130,000 times, liked 2,800 times and received 3,400 comments, the court was told.
Ms Hardcastle said the reference to another photograph being removed “demonstrates that there were two posts on that day”, making the February 2018 post “the third occasion on which she had purported to post a picture of Venables in three months”.
She said the contempt proceedings were not brought in relation to that post because of legal issues with her first police interview, but said it provided “essential context” for the later post.
Ms Hardcastle added it was “notable” the November 2017 post “included a photograph of a different man to the February 20 post”, and that McGuire had admitted in interview at least “one of those images must be wrong”.
She said the posts posed a risk of “serious harm” to Venables as well as “those mistakenly identified as Venables”.
It was “particularly troubling that two separate men seem to have been identified” as Venables, Lord Justice Davis said.
John Hipkin, representing McGuire, accepted “this is an extremely serious matter” but said there was “a real prospect of rehabilitation”.
He said McGuire had since withdrawn from all forms of social media.